Cellular communication systems are divided into a plurality of contiguous specific geographical coverage areas called cells. Access, via mobile subscriber (MS) radiotelephones, to the telephone network is through a cell site or macrocellular base station (BS) located in each cell, (i.e., equipment which includes antennas, radio transceivers and control equipment operative to facilitate radio air interconnection between a MS and the BS assigned to cover the geographical area where the MS is located). The BS is connected to a mobile switching center (MSC) which is in turn connected to the public switched land telephone network (PSTN). A detailed description of the cellular telecommunications system may be found in "The Cellular Concept" by V. H. MacDonald in The Bell System Technical Journal, January 1979, Vol. 58 No. 1, pages 15-42.
Coverage in the geographical area of a cell by a single BS is typically uneven. Due to topographical features and building structures and highway passageways; dead or weak spots exist within the cell's geographical area. Coverage of an MS within these dead or weak spots is either substandard or non-existent. MSs may fail to connect, may be suddenly disconnected or may experience a fading of transmission signals.
Coverage of a cell area may be readily enhanced by the utilization of microcells distributed among the dead or weak spots or in places needing enhanced capacity to handle MSs. Microcell access stations typically act as satellites or repeaters and are used to illuminate or radiate the dead or weak spots. The typical microcell access station includes amplifiers and radiation antennas. All other signal processing is performed at the BS. They are typically connected to the cell site or BS, via a high capacity link such as light fiber.
BSs operate with analog signal processing at present. The light fiber link is hence used to transmit analog signals between the BS and the microcell. These light fiber lines are frequently provided by a public utility whose tariff is based on a digital bit rate use. Hence transmitting analog signals becomes prohibitively expensive.